Method of making electrical switch contacts



Dec. 22, 1931. H, SIE MUND 1,837,238

METHOD OF MAKING ELECTRICAL SWITCH CONTACTS Filed Jan. 2, 1929 FIG. 4

BY W 71 tamed Dec. 22,, 193i HUME REYS 0. SIEGMUND, OF WEST ONGE, NEW JERfiEY, ASSIGNQR T0 BELL TELE- PHONE LABORATORIES, INCORPQBA'JLED', OF NEW YORK, N. Y., A. CORPOTION OF NEW YORK irn'rnon or MING unncrarcar. swrrcn con'rac'rs Application filed January 2, 1929. Serial No. 329,844.

such metals in the manufacture of these contactswhich required a minimum volume of material to present maxlmum area of coopera-ting contact surfaces and which function efficiently over wide ranges of operating conditions.

According to this invention a strip of base metal is first plated with a precious or semiprecious metal and a narrow strip of contact metal is united therewith. The plated backing metal prevents smutting of the contacting surfaces from side sparking. The method used for plating the base metal may be silver, gold or any precious or semi-precious metal.

By virtue of this invention, the use of expensive machinery and forming tools is eliminated, and economical utilization of all the precious metal contact material is effected.

The invention will be readily understood from the following detailed description made with reference to the accompanying drawings in which, v

Fig. 1 is an enlarged view of a strip of base metal having three of its surfaces electroplated;

Fig. 2 is an enlarged view of a strip of precious metal contact elements Fig. 3,is an enlarged view of a length of trimetal contact material before being cut into individual contact elements;

Fig. 4 is an enlarged view of an individual contact element;

Fig. 5 shows a contact element mounted on a switching element, such as a relay contact spring.

According to this invention a strip 10 shown in Fig. 1 of base metal, such as brass, and of the proper cross-sectional shape is provided preferably on three of its sides with a covering of semi-precious metal 11, such as silver, gold or any material having high meltmg point characteristic. This covering may be applied as by electro-deposition or in any other well-known manner.

On the plated side opposite to the unplated slde of strip 10 is welded a strip of precious metal shown in Fig. 2 having reduced portions 13 disposed at suitable intervals along the strip. These reduced portions define the length of the precious metal elements, and the formation of these elements in strip form, facilitate their welding on the base metal strip in proper relation to each other, after which the tri-metallic bar thus formed may be cut transversely in planes passing through the indentations in order to obtain contacts as shown in Fig. 4.. This contact may then be united as by welding to a supporting member such as 14 shown in Fig. 5. The cutting operation of the contacts from the strip, however, may conveniently be effected in subsequent operations to that of the welding operations of the contacts on their supporting members.

What is claimed is: 1

1. Th method of producing switch contacts which consists in plating three surfaces of a strip of base metal with contact metal, welding a strip of contact metal on one of the plated sides of the base metal and welding the base metal to a supporting element.

2. The method of .producing switch contacts which consists in welding a strip of contact metal to a bi-metallic strip, the bimetallic strip having portions extending on opposite sides of the contact metal strip, and welding a piece of the combined metal onthe supporting element.

The method of producing switch contacts which consists in plating three surfaces of a strip of base metal with contact metal, welding an indented strip of contact metal on one of the plated sides of the base metal, welding portions of the tri-metallic bar to supporting elements and cutting the bar transversely in planes passing through the indentations.

"In witness whereof, I hereunto subscribe my name this 31st day of December, 1928.

HUMPHREYS O. SIEGM'UND. 

